Bonneville Dam Fish Passage and Spillway

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Bonneville Dam Fish Passage and Spillway

Maintaining a National Historic Landmark dam to keep hydropower generation in motion.

For the past decade, we’ve supported the U.S. Army Corps of Engineers’ efforts to maintain Bonneville Dam. Designated a National Historic Landmark, the dam was built at the height of the Great Depression by the Corps.

When hydrographic surveys revealed serious erosion and cavitation concerns at the spillway and stilling basin, we prepared an alternatives analysis and report for the Corps to evaluate potential repairs and improvements, including those related to fish passage and total dissolved gas at the site.

Alternatives presented to the Corps include adjustable flow deflectors, spillway pier modifications, a spillwall and a forebay behavioral guidance structure. Each of these alternatives presented numerous challenges ranging from major structural, mechanical and durability complexities to geotechnical issues associated with a 100-foot-tall, 1500-foot-long spill wall. General operational, maintenance and safety issues were associated with each alternative.

Through a collaborative design process, we developed viable alternatives for each of the design concepts. Our team established a cost estimate and conducted a constructability review to help the Corps and regulatory agencies make informed decisions.